The Rustrictor Field/Ammo Box Small is the premium .30 cal ammo box out there. As soon as you hear the secure snap of the brass-bailed latch, Rustrictor technology turns the interior of the field box into a rust-blocking vortex. The water-resistant O-ring seal adds another layer of protection. Put all that together, and up to 8 boxes of .30 caliber ammo (or whatever else you put inside) remain quadruple protected from water, dust, rust and corrosion.